/* * Interface for controlling IO bandwidth on a request queue * * Copyright (C) 2010 Vivek Goyal <vgoyal@redhat.com> */ #include <linux/module.h> #include <linux/slab.h> #include <linux/blkdev.h> #include <linux/bio.h> #include <linux/blktrace_api.h> #include "blk-cgroup.h" #include "blk.h" /* Max dispatch from a group in 1 round */ static int throtl_grp_quantum = 8; /* Total max dispatch from all groups in one round */ static int throtl_quantum = 32; /* Throttling is performed over 100ms slice and after that slice is renewed */ static unsigned long throtl_slice = HZ/10; /* 100 ms */ static struct blkcg_policy blkcg_policy_throtl; /* A workqueue to queue throttle related work */ static struct workqueue_struct *kthrotld_workqueue; static void throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay); struct throtl_rb_root { struct rb_root rb; struct rb_node *left; unsigned int count; unsigned long min_disptime; }; #define THROTL_RB_ROOT (struct throtl_rb_root) { .rb = RB_ROOT, .left = NULL, \ .count = 0, .min_disptime = 0} #define rb_entry_tg(node) rb_entry((node), struct throtl_grp, rb_node) /* Per-cpu group stats */ struct tg_stats_cpu { /* total bytes transferred */ struct blkg_rwstat service_bytes; /* total IOs serviced, post merge */ struct blkg_rwstat serviced; }; struct throtl_grp { /* must be the first member */ struct blkg_policy_data pd; /* active throtl group service_tree member */ struct rb_node rb_node; /* * Dispatch time in jiffies. This is the estimated time when group * will unthrottle and is ready to dispatch more bio. It is used as * key to sort active groups in service tree. */ unsigned long disptime; unsigned int flags; /* Two lists for READ and WRITE */ struct bio_list bio_lists[2]; /* Number of queued bios on READ and WRITE lists */ unsigned int nr_queued[2]; /* bytes per second rate limits */ uint64_t bps[2]; /* IOPS limits */ unsigned int iops[2]; /* Number of bytes disptached in current slice */ uint64_t bytes_disp[2]; /* Number of bio's dispatched in current slice */ unsigned int io_disp[2]; /* When did we start a new slice */ unsigned long slice_start[2]; unsigned long slice_end[2]; /* Some throttle limits got updated for the group */ int limits_changed; /* Per cpu stats pointer */ struct tg_stats_cpu __percpu *stats_cpu; /* List of tgs waiting for per cpu stats memory to be allocated */ struct list_head stats_alloc_node; }; struct throtl_data { /* service tree for active throtl groups */ struct throtl_rb_root tg_service_tree; struct request_queue *queue; /* Total Number of queued bios on READ and WRITE lists */ unsigned int nr_queued[2]; /* * number of total undestroyed groups */ unsigned int nr_undestroyed_grps; /* Work for dispatching throttled bios */ struct delayed_work throtl_work; int limits_changed; }; /* list and work item to allocate percpu group stats */ static DEFINE_SPINLOCK(tg_stats_alloc_lock); static LIST_HEAD(tg_stats_alloc_list); static void tg_stats_alloc_fn(struct work_struct *); static DECLARE_DELAYED_WORK(tg_stats_alloc_work, tg_stats_alloc_fn); static inline struct throtl_grp *pd_to_tg(struct blkg_policy_data *pd) { return pd ? container_of(pd, struct throtl_grp, pd) : NULL; } static inline struct throtl_grp *blkg_to_tg(struct blkcg_gq *blkg) { return pd_to_tg(blkg_to_pd(blkg, &blkcg_policy_throtl)); } static inline struct blkcg_gq *tg_to_blkg(struct throtl_grp *tg) { return pd_to_blkg(&tg->pd); } static inline struct throtl_grp *td_root_tg(struct throtl_data *td) { return blkg_to_tg(td->queue->root_blkg); } enum tg_state_flags { THROTL_TG_FLAG_on_rr = 0, /* on round-robin busy list */ }; #define THROTL_TG_FNS(name) \ static inline void throtl_mark_tg_##name(struct throtl_grp *tg) \ { \ (tg)->flags |= (1 << THROTL_TG_FLAG_##name); \ } \ static inline void throtl_clear_tg_##name(struct throtl_grp *tg) \ { \ (tg)->flags &= ~(1 << THROTL_TG_FLAG_##name); \ } \ static inline int throtl_tg_##name(const struct throtl_grp *tg) \ { \ return ((tg)->flags & (1 << THROTL_TG_FLAG_##name)) != 0; \ } THROTL_TG_FNS(on_rr); #define throtl_log_tg(td, tg, fmt, args...) do { \ char __pbuf[128]; \ \ blkg_path(tg_to_blkg(tg), __pbuf, sizeof(__pbuf)); \ blk_add_trace_msg((td)->queue, "throtl %s " fmt, __pbuf, ##args); \ } while (0) #define throtl_log(td, fmt, args...) \ blk_add_trace_msg((td)->queue, "throtl " fmt, ##args) static inline unsigned int total_nr_queued(struct throtl_data *td) { return td->nr_queued[0] + td->nr_queued[1]; } /* * Worker for allocating per cpu stat for tgs. This is scheduled on the * system_wq once there are some groups on the alloc_list waiting for * allocation. */ static void tg_stats_alloc_fn(struct work_struct *work) { static struct tg_stats_cpu *stats_cpu; /* this fn is non-reentrant */ struct delayed_work *dwork = to_delayed_work(work); bool empty = false; alloc_stats: if (!stats_cpu) { stats_cpu = alloc_percpu(struct tg_stats_cpu); if (!stats_cpu) { /* allocation failed, try again after some time */ schedule_delayed_work(dwork, msecs_to_jiffies(10)); return; } } spin_lock_irq(&tg_stats_alloc_lock); if (!list_empty(&tg_stats_alloc_list)) { struct throtl_grp *tg = list_first_entry(&tg_stats_alloc_list, struct throtl_grp, stats_alloc_node); swap(tg->stats_cpu, stats_cpu); list_del_init(&tg->stats_alloc_node); } empty = list_empty(&tg_stats_alloc_list); spin_unlock_irq(&tg_stats_alloc_lock); if (!empty) goto alloc_stats; } static void throtl_pd_init(struct blkcg_gq *blkg) { struct throtl_grp *tg = blkg_to_tg(blkg); unsigned long flags; RB_CLEAR_NODE(&tg->rb_node); bio_list_init(&tg->bio_lists[0]); bio_list_init(&tg->bio_lists[1]); tg->limits_changed = false; tg->bps[READ] = -1; tg->bps[WRITE] = -1; tg->iops[READ] = -1; tg->iops[WRITE] = -1; /* * Ugh... We need to perform per-cpu allocation for tg->stats_cpu * but percpu allocator can't be called from IO path. Queue tg on * tg_stats_alloc_list and allocate from work item. */ spin_lock_irqsave(&tg_stats_alloc_lock, flags); list_add(&tg->stats_alloc_node, &tg_stats_alloc_list); schedule_delayed_work(&tg_stats_alloc_work, 0); spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); } static void throtl_pd_exit(struct blkcg_gq *blkg) { struct throtl_grp *tg = blkg_to_tg(blkg); unsigned long flags; spin_lock_irqsave(&tg_stats_alloc_lock, flags); list_del_init(&tg->stats_alloc_node); spin_unlock_irqrestore(&tg_stats_alloc_lock, flags); free_percpu(tg->stats_cpu); } static void throtl_pd_reset_stats(struct blkcg_gq *blkg) { struct throtl_grp *tg = blkg_to_tg(blkg); int cpu; if (tg->stats_cpu == NULL) return; for_each_possible_cpu(cpu) { struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); blkg_rwstat_reset(&sc->service_bytes); blkg_rwstat_reset(&sc->serviced); } } static struct throtl_grp *throtl_lookup_tg(struct throtl_data *td, struct blkcg *blkcg) { /* * This is the common case when there are no blkcgs. Avoid lookup * in this case */ if (blkcg == &blkcg_root) return td_root_tg(td); return blkg_to_tg(blkg_lookup(blkcg, td->queue)); } static struct throtl_grp *throtl_lookup_create_tg(struct throtl_data *td, struct blkcg *blkcg) { struct request_queue *q = td->queue; struct throtl_grp *tg = NULL; /* * This is the common case when there are no blkcgs. Avoid lookup * in this case */ if (blkcg == &blkcg_root) { tg = td_root_tg(td); } else { struct blkcg_gq *blkg; blkg = blkg_lookup_create(blkcg, q); /* if %NULL and @q is alive, fall back to root_tg */ if (!IS_ERR(blkg)) tg = blkg_to_tg(blkg); else if (!blk_queue_dead(q)) tg = td_root_tg(td); } return tg; } static struct throtl_grp *throtl_rb_first(struct throtl_rb_root *root) { /* Service tree is empty */ if (!root->count) return NULL; if (!root->left) root->left = rb_first(&root->rb); if (root->left) return rb_entry_tg(root->left); return NULL; } static void rb_erase_init(struct rb_node *n, struct rb_root *root) { rb_erase(n, root); RB_CLEAR_NODE(n); } static void throtl_rb_erase(struct rb_node *n, struct throtl_rb_root *root) { if (root->left == n) root->left = NULL; rb_erase_init(n, &root->rb); --root->count; } static void update_min_dispatch_time(struct throtl_rb_root *st) { struct throtl_grp *tg; tg = throtl_rb_first(st); if (!tg) return; st->min_disptime = tg->disptime; } static void tg_service_tree_add(struct throtl_rb_root *st, struct throtl_grp *tg) { struct rb_node **node = &st->rb.rb_node; struct rb_node *parent = NULL; struct throtl_grp *__tg; unsigned long key = tg->disptime; int left = 1; while (*node != NULL) { parent = *node; __tg = rb_entry_tg(parent); if (time_before(key, __tg->disptime)) node = &parent->rb_left; else { node = &parent->rb_right; left = 0; } } if (left) st->left = &tg->rb_node; rb_link_node(&tg->rb_node, parent, node); rb_insert_color(&tg->rb_node, &st->rb); } static void __throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) { struct throtl_rb_root *st = &td->tg_service_tree; tg_service_tree_add(st, tg); throtl_mark_tg_on_rr(tg); st->count++; } static void throtl_enqueue_tg(struct throtl_data *td, struct throtl_grp *tg) { if (!throtl_tg_on_rr(tg)) __throtl_enqueue_tg(td, tg); } static void __throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) { throtl_rb_erase(&tg->rb_node, &td->tg_service_tree); throtl_clear_tg_on_rr(tg); } static void throtl_dequeue_tg(struct throtl_data *td, struct throtl_grp *tg) { if (throtl_tg_on_rr(tg)) __throtl_dequeue_tg(td, tg); } static void throtl_schedule_next_dispatch(struct throtl_data *td) { struct throtl_rb_root *st = &td->tg_service_tree; /* * If there are more bios pending, schedule more work. */ if (!total_nr_queued(td)) return; BUG_ON(!st->count); update_min_dispatch_time(st); if (time_before_eq(st->min_disptime, jiffies)) throtl_schedule_delayed_work(td, 0); else throtl_schedule_delayed_work(td, (st->min_disptime - jiffies)); } static inline void throtl_start_new_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) { tg->bytes_disp[rw] = 0; tg->io_disp[rw] = 0; tg->slice_start[rw] = jiffies; tg->slice_end[rw] = jiffies + throtl_slice; throtl_log_tg(td, tg, "[%c] new slice start=%lu end=%lu jiffies=%lu", rw == READ ? 'R' : 'W', tg->slice_start[rw], tg->slice_end[rw], jiffies); } static inline void throtl_set_slice_end(struct throtl_data *td, struct throtl_grp *tg, bool rw, unsigned long jiffy_end) { tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); } static inline void throtl_extend_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw, unsigned long jiffy_end) { tg->slice_end[rw] = roundup(jiffy_end, throtl_slice); throtl_log_tg(td, tg, "[%c] extend slice start=%lu end=%lu jiffies=%lu", rw == READ ? 'R' : 'W', tg->slice_start[rw], tg->slice_end[rw], jiffies); } /* Determine if previously allocated or extended slice is complete or not */ static bool throtl_slice_used(struct throtl_data *td, struct throtl_grp *tg, bool rw) { if (time_in_range(jiffies, tg->slice_start[rw], tg->slice_end[rw])) return 0; return 1; } /* Trim the used slices and adjust slice start accordingly */ static inline void throtl_trim_slice(struct throtl_data *td, struct throtl_grp *tg, bool rw) { unsigned long nr_slices, time_elapsed, io_trim; u64 bytes_trim, tmp; BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])); /* * If bps are unlimited (-1), then time slice don't get * renewed. Don't try to trim the slice if slice is used. A new * slice will start when appropriate. */ if (throtl_slice_used(td, tg, rw)) return; /* * A bio has been dispatched. Also adjust slice_end. It might happen * that initially cgroup limit was very low resulting in high * slice_end, but later limit was bumped up and bio was dispached * sooner, then we need to reduce slice_end. A high bogus slice_end * is bad because it does not allow new slice to start. */ throtl_set_slice_end(td, tg, rw, jiffies + throtl_slice); time_elapsed = jiffies - tg->slice_start[rw]; nr_slices = time_elapsed / throtl_slice; if (!nr_slices) return; tmp = tg->bps[rw] * throtl_slice * nr_slices; do_div(tmp, HZ); bytes_trim = tmp; io_trim = (tg->iops[rw] * throtl_slice * nr_slices)/HZ; if (!bytes_trim && !io_trim) return; if (tg->bytes_disp[rw] >= bytes_trim) tg->bytes_disp[rw] -= bytes_trim; else tg->bytes_disp[rw] = 0; if (tg->io_disp[rw] >= io_trim) tg->io_disp[rw] -= io_trim; else tg->io_disp[rw] = 0; tg->slice_start[rw] += nr_slices * throtl_slice; throtl_log_tg(td, tg, "[%c] trim slice nr=%lu bytes=%llu io=%lu" " start=%lu end=%lu jiffies=%lu", rw == READ ? 'R' : 'W', nr_slices, bytes_trim, io_trim, tg->slice_start[rw], tg->slice_end[rw], jiffies); } static bool tg_with_in_iops_limit(struct throtl_data *td, struct throtl_grp *tg, struct bio *bio, unsigned long *wait) { bool rw = bio_data_dir(bio); unsigned int io_allowed; unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; u64 tmp; jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; /* Slice has just started. Consider one slice interval */ if (!jiffy_elapsed) jiffy_elapsed_rnd = throtl_slice; jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); /* * jiffy_elapsed_rnd should not be a big value as minimum iops can be * 1 then at max jiffy elapsed should be equivalent of 1 second as we * will allow dispatch after 1 second and after that slice should * have been trimmed. */ tmp = (u64)tg->iops[rw] * jiffy_elapsed_rnd; do_div(tmp, HZ); if (tmp > UINT_MAX) io_allowed = UINT_MAX; else io_allowed = tmp; if (tg->io_disp[rw] + 1 <= io_allowed) { if (wait) *wait = 0; return 1; } /* Calc approx time to dispatch */ jiffy_wait = ((tg->io_disp[rw] + 1) * HZ)/tg->iops[rw] + 1; if (jiffy_wait > jiffy_elapsed) jiffy_wait = jiffy_wait - jiffy_elapsed; else jiffy_wait = 1; if (wait) *wait = jiffy_wait; return 0; } static bool tg_with_in_bps_limit(struct throtl_data *td, struct throtl_grp *tg, struct bio *bio, unsigned long *wait) { bool rw = bio_data_dir(bio); u64 bytes_allowed, extra_bytes, tmp; unsigned long jiffy_elapsed, jiffy_wait, jiffy_elapsed_rnd; jiffy_elapsed = jiffy_elapsed_rnd = jiffies - tg->slice_start[rw]; /* Slice has just started. Consider one slice interval */ if (!jiffy_elapsed) jiffy_elapsed_rnd = throtl_slice; jiffy_elapsed_rnd = roundup(jiffy_elapsed_rnd, throtl_slice); tmp = tg->bps[rw] * jiffy_elapsed_rnd; do_div(tmp, HZ); bytes_allowed = tmp; if (tg->bytes_disp[rw] + bio->bi_size <= bytes_allowed) { if (wait) *wait = 0; return 1; } /* Calc approx time to dispatch */ extra_bytes = tg->bytes_disp[rw] + bio->bi_size - bytes_allowed; jiffy_wait = div64_u64(extra_bytes * HZ, tg->bps[rw]); if (!jiffy_wait) jiffy_wait = 1; /* * This wait time is without taking into consideration the rounding * up we did. Add that time also. */ jiffy_wait = jiffy_wait + (jiffy_elapsed_rnd - jiffy_elapsed); if (wait) *wait = jiffy_wait; return 0; } static bool tg_no_rule_group(struct throtl_grp *tg, bool rw) { if (tg->bps[rw] == -1 && tg->iops[rw] == -1) return 1; return 0; } /* * Returns whether one can dispatch a bio or not. Also returns approx number * of jiffies to wait before this bio is with-in IO rate and can be dispatched */ static bool tg_may_dispatch(struct throtl_data *td, struct throtl_grp *tg, struct bio *bio, unsigned long *wait) { bool rw = bio_data_dir(bio); unsigned long bps_wait = 0, iops_wait = 0, max_wait = 0; /* * Currently whole state machine of group depends on first bio * queued in the group bio list. So one should not be calling * this function with a different bio if there are other bios * queued. */ BUG_ON(tg->nr_queued[rw] && bio != bio_list_peek(&tg->bio_lists[rw])); /* If tg->bps = -1, then BW is unlimited */ if (tg->bps[rw] == -1 && tg->iops[rw] == -1) { if (wait) *wait = 0; return 1; } /* * If previous slice expired, start a new one otherwise renew/extend * existing slice to make sure it is at least throtl_slice interval * long since now. */ if (throtl_slice_used(td, tg, rw)) throtl_start_new_slice(td, tg, rw); else { if (time_before(tg->slice_end[rw], jiffies + throtl_slice)) throtl_extend_slice(td, tg, rw, jiffies + throtl_slice); } if (tg_with_in_bps_limit(td, tg, bio, &bps_wait) && tg_with_in_iops_limit(td, tg, bio, &iops_wait)) { if (wait) *wait = 0; return 1; } max_wait = max(bps_wait, iops_wait); if (wait) *wait = max_wait; if (time_before(tg->slice_end[rw], jiffies + max_wait)) throtl_extend_slice(td, tg, rw, jiffies + max_wait); return 0; } static void throtl_update_dispatch_stats(struct blkcg_gq *blkg, u64 bytes, int rw) { struct throtl_grp *tg = blkg_to_tg(blkg); struct tg_stats_cpu *stats_cpu; unsigned long flags; /* If per cpu stats are not allocated yet, don't do any accounting. */ if (tg->stats_cpu == NULL) return; /* * Disabling interrupts to provide mutual exclusion between two * writes on same cpu. It probably is not needed for 64bit. Not * optimizing that case yet. */ local_irq_save(flags); stats_cpu = this_cpu_ptr(tg->stats_cpu); blkg_rwstat_add(&stats_cpu->serviced, rw, 1); blkg_rwstat_add(&stats_cpu->service_bytes, rw, bytes); local_irq_restore(flags); } static void throtl_charge_bio(struct throtl_grp *tg, struct bio *bio) { bool rw = bio_data_dir(bio); /* Charge the bio to the group */ tg->bytes_disp[rw] += bio->bi_size; tg->io_disp[rw]++; throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw); } static void throtl_add_bio_tg(struct throtl_data *td, struct throtl_grp *tg, struct bio *bio) { bool rw = bio_data_dir(bio); bio_list_add(&tg->bio_lists[rw], bio); /* Take a bio reference on tg */ blkg_get(tg_to_blkg(tg)); tg->nr_queued[rw]++; td->nr_queued[rw]++; throtl_enqueue_tg(td, tg); } static void tg_update_disptime(struct throtl_data *td, struct throtl_grp *tg) { unsigned long read_wait = -1, write_wait = -1, min_wait = -1, disptime; struct bio *bio; if ((bio = bio_list_peek(&tg->bio_lists[READ]))) tg_may_dispatch(td, tg, bio, &read_wait); if ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) tg_may_dispatch(td, tg, bio, &write_wait); min_wait = min(read_wait, write_wait); disptime = jiffies + min_wait; /* Update dispatch time */ throtl_dequeue_tg(td, tg); tg->disptime = disptime; throtl_enqueue_tg(td, tg); } static void tg_dispatch_one_bio(struct throtl_data *td, struct throtl_grp *tg, bool rw, struct bio_list *bl) { struct bio *bio; bio = bio_list_pop(&tg->bio_lists[rw]); tg->nr_queued[rw]--; /* Drop bio reference on blkg */ blkg_put(tg_to_blkg(tg)); BUG_ON(td->nr_queued[rw] <= 0); td->nr_queued[rw]--; throtl_charge_bio(tg, bio); bio_list_add(bl, bio); bio->bi_rw |= REQ_THROTTLED; throtl_trim_slice(td, tg, rw); } static int throtl_dispatch_tg(struct throtl_data *td, struct throtl_grp *tg, struct bio_list *bl) { unsigned int nr_reads = 0, nr_writes = 0; unsigned int max_nr_reads = throtl_grp_quantum*3/4; unsigned int max_nr_writes = throtl_grp_quantum - max_nr_reads; struct bio *bio; /* Try to dispatch 75% READS and 25% WRITES */ while ((bio = bio_list_peek(&tg->bio_lists[READ])) && tg_may_dispatch(td, tg, bio, NULL)) { tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); nr_reads++; if (nr_reads >= max_nr_reads) break; } while ((bio = bio_list_peek(&tg->bio_lists[WRITE])) && tg_may_dispatch(td, tg, bio, NULL)) { tg_dispatch_one_bio(td, tg, bio_data_dir(bio), bl); nr_writes++; if (nr_writes >= max_nr_writes) break; } return nr_reads + nr_writes; } static int throtl_select_dispatch(struct throtl_data *td, struct bio_list *bl) { unsigned int nr_disp = 0; struct throtl_grp *tg; struct throtl_rb_root *st = &td->tg_service_tree; while (1) { tg = throtl_rb_first(st); if (!tg) break; if (time_before(jiffies, tg->disptime)) break; throtl_dequeue_tg(td, tg); nr_disp += throtl_dispatch_tg(td, tg, bl); if (tg->nr_queued[0] || tg->nr_queued[1]) { tg_update_disptime(td, tg); throtl_enqueue_tg(td, tg); } if (nr_disp >= throtl_quantum) break; } return nr_disp; } static void throtl_process_limit_change(struct throtl_data *td) { struct request_queue *q = td->queue; struct blkcg_gq *blkg, *n; if (!td->limits_changed) return; xchg(&td->limits_changed, false); throtl_log(td, "limits changed"); list_for_each_entry_safe(blkg, n, &q->blkg_list, q_node) { struct throtl_grp *tg = blkg_to_tg(blkg); if (!tg->limits_changed) continue; if (!xchg(&tg->limits_changed, false)) continue; throtl_log_tg(td, tg, "limit change rbps=%llu wbps=%llu" " riops=%u wiops=%u", tg->bps[READ], tg->bps[WRITE], tg->iops[READ], tg->iops[WRITE]); /* * Restart the slices for both READ and WRITES. It * might happen that a group's limit are dropped * suddenly and we don't want to account recently * dispatched IO with new low rate */ throtl_start_new_slice(td, tg, 0); throtl_start_new_slice(td, tg, 1); if (throtl_tg_on_rr(tg)) tg_update_disptime(td, tg); } } /* Dispatch throttled bios. Should be called without queue lock held. */ static int throtl_dispatch(struct request_queue *q) { struct throtl_data *td = q->td; unsigned int nr_disp = 0; struct bio_list bio_list_on_stack; struct bio *bio; struct blk_plug plug; spin_lock_irq(q->queue_lock); throtl_process_limit_change(td); if (!total_nr_queued(td)) goto out; bio_list_init(&bio_list_on_stack); throtl_log(td, "dispatch nr_queued=%u read=%u write=%u", total_nr_queued(td), td->nr_queued[READ], td->nr_queued[WRITE]); nr_disp = throtl_select_dispatch(td, &bio_list_on_stack); if (nr_disp) throtl_log(td, "bios disp=%u", nr_disp); throtl_schedule_next_dispatch(td); out: spin_unlock_irq(q->queue_lock); /* * If we dispatched some requests, unplug the queue to make sure * immediate dispatch */ if (nr_disp) { blk_start_plug(&plug); while((bio = bio_list_pop(&bio_list_on_stack))) generic_make_request(bio); blk_finish_plug(&plug); } return nr_disp; } void blk_throtl_work(struct work_struct *work) { struct throtl_data *td = container_of(work, struct throtl_data, throtl_work.work); struct request_queue *q = td->queue; throtl_dispatch(q); } /* Call with queue lock held */ static void throtl_schedule_delayed_work(struct throtl_data *td, unsigned long delay) { struct delayed_work *dwork = &td->throtl_work; /* schedule work if limits changed even if no bio is queued */ if (total_nr_queued(td) || td->limits_changed) { mod_delayed_work(kthrotld_workqueue, dwork, delay); throtl_log(td, "schedule work. delay=%lu jiffies=%lu", delay, jiffies); } } static u64 tg_prfill_cpu_rwstat(struct seq_file *sf, struct blkg_policy_data *pd, int off) { struct throtl_grp *tg = pd_to_tg(pd); struct blkg_rwstat rwstat = { }, tmp; int i, cpu; for_each_possible_cpu(cpu) { struct tg_stats_cpu *sc = per_cpu_ptr(tg->stats_cpu, cpu); tmp = blkg_rwstat_read((void *)sc + off); for (i = 0; i < BLKG_RWSTAT_NR; i++) rwstat.cnt[i] += tmp.cnt[i]; } return __blkg_prfill_rwstat(sf, pd, &rwstat); } static int tg_print_cpu_rwstat(struct cgroup *cgrp, struct cftype *cft, struct seq_file *sf) { struct blkcg *blkcg = cgroup_to_blkcg(cgrp); blkcg_print_blkgs(sf, blkcg, tg_prfill_cpu_rwstat, &blkcg_policy_throtl, cft->private, true); return 0; } static u64 tg_prfill_conf_u64(struct seq_file *sf, struct blkg_policy_data *pd, int off) { struct throtl_grp *tg = pd_to_tg(pd); u64 v = *(u64 *)((void *)tg + off); if (v == -1) return 0; return __blkg_prfill_u64(sf, pd, v); } static u64 tg_prfill_conf_uint(struct seq_file *sf, struct blkg_policy_data *pd, int off) { struct throtl_grp *tg = pd_to_tg(pd); unsigned int v = *(unsigned int *)((void *)tg + off); if (v == -1) return 0; return __blkg_prfill_u64(sf, pd, v); } static int tg_print_conf_u64(struct cgroup *cgrp, struct cftype *cft, struct seq_file *sf) { blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_u64, &blkcg_policy_throtl, cft->private, false); return 0; } static int tg_print_conf_uint(struct cgroup *cgrp, struct cftype *cft, struct seq_file *sf) { blkcg_print_blkgs(sf, cgroup_to_blkcg(cgrp), tg_prfill_conf_uint, &blkcg_policy_throtl, cft->private, false); return 0; } static int tg_set_conf(struct cgroup *cgrp, struct cftype *cft, const char *buf, bool is_u64) { struct blkcg *blkcg = cgroup_to_blkcg(cgrp); struct blkg_conf_ctx ctx; struct throtl_grp *tg; struct throtl_data *td; int ret; ret = blkg_conf_prep(blkcg, &blkcg_policy_throtl, buf, &ctx); if (ret) return ret; tg = blkg_to_tg(ctx.blkg); td = ctx.blkg->q->td; if (!ctx.v) ctx.v = -1; if (is_u64) *(u64 *)((void *)tg + cft->private) = ctx.v; else *(unsigned int *)((void *)tg + cft->private) = ctx.v; /* XXX: we don't need the following deferred processing */ xchg(&tg->limits_changed, true); xchg(&td->limits_changed, true); throtl_schedule_delayed_work(td, 0); blkg_conf_finish(&ctx); return 0; } static int tg_set_conf_u64(struct cgroup *cgrp, struct cftype *cft, const char *buf) { return tg_set_conf(cgrp, cft, buf, true); } static int tg_set_conf_uint(struct cgroup *cgrp, struct cftype *cft, const char *buf) { return tg_set_conf(cgrp, cft, buf, false); } static struct cftype throtl_files[] = { { .name = "throttle.read_bps_device", .private = offsetof(struct throtl_grp, bps[READ]), .read_seq_string = tg_print_conf_u64, .write_string = tg_set_conf_u64, .max_write_len = 256, }, { .name = "throttle.write_bps_device", .private = offsetof(struct throtl_grp, bps[WRITE]), .read_seq_string = tg_print_conf_u64, .write_string = tg_set_conf_u64, .max_write_len = 256, }, { .name = "throttle.read_iops_device", .private = offsetof(struct throtl_grp, iops[READ]), .read_seq_string = tg_print_conf_uint, .write_string = tg_set_conf_uint, .max_write_len = 256, }, { .name = "throttle.write_iops_device", .private = offsetof(struct throtl_grp, iops[WRITE]), .read_seq_string = tg_print_conf_uint, .write_string = tg_set_conf_uint, .max_write_len = 256, }, { .name = "throttle.io_service_bytes", .private = offsetof(struct tg_stats_cpu, service_bytes), .read_seq_string = tg_print_cpu_rwstat, }, { .name = "throttle.io_serviced", .private = offsetof(struct tg_stats_cpu, serviced), .read_seq_string = tg_print_cpu_rwstat, }, { } /* terminate */ }; static void throtl_shutdown_wq(struct request_queue *q) { struct throtl_data *td = q->td; cancel_delayed_work_sync(&td->throtl_work); } static struct blkcg_policy blkcg_policy_throtl = { .pd_size = sizeof(struct throtl_grp), .cftypes = throtl_files, .pd_init_fn = throtl_pd_init, .pd_exit_fn = throtl_pd_exit, .pd_reset_stats_fn = throtl_pd_reset_stats, }; bool blk_throtl_bio(struct request_queue *q, struct bio *bio) { struct throtl_data *td = q->td; struct throtl_grp *tg; bool rw = bio_data_dir(bio), update_disptime = true; struct blkcg *blkcg; bool throttled = false; if (bio->bi_rw & REQ_THROTTLED) { bio->bi_rw &= ~REQ_THROTTLED; goto out; } /* * A throtl_grp pointer retrieved under rcu can be used to access * basic fields like stats and io rates. If a group has no rules, * just update the dispatch stats in lockless manner and return. */ rcu_read_lock(); blkcg = bio_blkcg(bio); tg = throtl_lookup_tg(td, blkcg); if (tg) { if (tg_no_rule_group(tg, rw)) { throtl_update_dispatch_stats(tg_to_blkg(tg), bio->bi_size, bio->bi_rw); goto out_unlock_rcu; } } /* * Either group has not been allocated yet or it is not an unlimited * IO group */ spin_lock_irq(q->queue_lock); tg = throtl_lookup_create_tg(td, blkcg); if (unlikely(!tg)) goto out_unlock; if (tg->nr_queued[rw]) { /* * There is already another bio queued in same dir. No * need to update dispatch time. */ update_disptime = false; goto queue_bio; } /* Bio is with-in rate limit of group */ if (tg_may_dispatch(td, tg, bio, NULL)) { throtl_charge_bio(tg, bio); /* * We need to trim slice even when bios are not being queued * otherwise it might happen that a bio is not queued for * a long time and slice keeps on extending and trim is not * called for a long time. Now if limits are reduced suddenly * we take into account all the IO dispatched so far at new * low rate and * newly queued IO gets a really long dispatch * time. * * So keep on trimming slice even if bio is not queued. */ throtl_trim_slice(td, tg, rw); goto out_unlock; } queue_bio: throtl_log_tg(td, tg, "[%c] bio. bdisp=%llu sz=%u bps=%llu" " iodisp=%u iops=%u queued=%d/%d", rw == READ ? 'R' : 'W', tg->bytes_disp[rw], bio->bi_size, tg->bps[rw], tg->io_disp[rw], tg->iops[rw], tg->nr_queued[READ], tg->nr_queued[WRITE]); bio_associate_current(bio); throtl_add_bio_tg(q->td, tg, bio); throttled = true; if (update_disptime) { tg_update_disptime(td, tg); throtl_schedule_next_dispatch(td); } out_unlock: spin_unlock_irq(q->queue_lock); out_unlock_rcu: rcu_read_unlock(); out: return throttled; } /** * blk_throtl_drain - drain throttled bios * @q: request_queue to drain throttled bios for * * Dispatch all currently throttled bios on @q through ->make_request_fn(). */ void blk_throtl_drain(struct request_queue *q) __releases(q->queue_lock) __acquires(q->queue_lock) { struct throtl_data *td = q->td; struct throtl_rb_root *st = &td->tg_service_tree; struct throtl_grp *tg; struct bio_list bl; struct bio *bio; queue_lockdep_assert_held(q); bio_list_init(&bl); while ((tg = throtl_rb_first(st))) { throtl_dequeue_tg(td, tg); while ((bio = bio_list_peek(&tg->bio_lists[READ]))) tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl); while ((bio = bio_list_peek(&tg->bio_lists[WRITE]))) tg_dispatch_one_bio(td, tg, bio_data_dir(bio), &bl); } spin_unlock_irq(q->queue_lock); while ((bio = bio_list_pop(&bl))) generic_make_request(bio); spin_lock_irq(q->queue_lock); } int blk_throtl_init(struct request_queue *q) { struct throtl_data *td; int ret; td = kzalloc_node(sizeof(*td), GFP_KERNEL, q->node); if (!td) return -ENOMEM; td->tg_service_tree = THROTL_RB_ROOT; td->limits_changed = false; INIT_DELAYED_WORK(&td->throtl_work, blk_throtl_work); q->td = td; td->queue = q; /* activate policy */ ret = blkcg_activate_policy(q, &blkcg_policy_throtl); if (ret) kfree(td); return ret; } void blk_throtl_exit(struct request_queue *q) { BUG_ON(!q->td); throtl_shutdown_wq(q); blkcg_deactivate_policy(q, &blkcg_policy_throtl); kfree(q->td); } static int __init throtl_init(void) { kthrotld_workqueue = alloc_workqueue("kthrotld", WQ_MEM_RECLAIM, 0); if (!kthrotld_workqueue) panic("Failed to create kthrotld\n"); return blkcg_policy_register(&blkcg_policy_throtl); } module_init(throtl_init);